This book focuses on the design, materials, process, fabrication, and reliability of flip chip, hybrid bonding, fan-in, and fan-out technology. Both principles and engineering practice have been addressed, with more weight placed on engineering practice. This is achieved by providing in-depth study on a number of major topics such as wafer bumping, flip chip assembly, underfill and reliability, chip-to-wafer, wafer-to-wafer, Cu-Cu hybrid bonding, WLCSP, 6-side molded WLCSP, FOWLP such as hybrid substrates with PID, ABF, and ultra-large organic interposer, the communications between chiplets and heterogeneous integration packaging, and on-board optics, near-package optics, and co-packaged optics. The book benefits researchers, engineers, and graduate students in the fields of electrical engineering, mechanical engineering, materials sciences, industry engineering, etc.